Abstract Multiple sclerosis (MS) is a T-cell mediated autoimmune disorder of the central nervous system. Current treatment strategies for MS are predominated by injectable therapies that do not target an underlying cause of the disease, have modest efficacy and have high cost and/or side effects that limit tolerability and compliance. An oral therapy that promotes self-tolerance by targeting an underlying disease mechanism, rather than broad and nonspecific immunosuppression, remains a major unmet need for the management of MS. As a complex trait disease, multiple genetic and environmental factors combine to influence disease risk in MS. Our published data in both mice and humans indicates that multiple genetic and environmental risk factors for MS converge to dysregulate protein N-glycosylation, thereby driving pathogenic autoimmune T cell responses. Therapeutic supplementation to N-glycan biosynthesis may provide the first therapy directly targeting an underlying cause of the disease. Indeed, supplementing the Golgi with the simple sugar N- acetylglucosamine (GlcNAc) rescues N-glycan branching deficiency in T cells by increasing metabolic supply of substrate to the Golgi enzymes, suppresses T cell growth and autoimmune T cell responses, prevents and treats mouse models of MS and/or autoimmune diabetes and improved disease in 8 of 12 human children with treatment-resistant inflammatory bowel disease. However, as a drug development target, GlcNAc has significant limitations. GlcNAc has poor membrane permeability, requiring high concentrations (40-80mM in vitro) for biological effects. To address this issue, we have developed novel analogs of GlcNAc that increase membrane permeability yet are converted back to GlcNAc by endogenous enzymes after entry into the cytoplasm. In preliminary studies, we have identified GlcNAc analogs that are effective at ~40,000 fold lower concentrations than GlcNAc in vitro, yet increase N-glycan branching with ~2 fold greater magnitude. The proposed project will examine differentially modified GlcNAc derivatives, for increased biological activity and efficacy in vitro and therapeutic efficacy in vivo. Specific Aim 1 will investigate GlcNAc analogs for optimal enhancement of N-glycan branching in vitro in mouse and human T cells. Specific Aim 2 will investigate GlcNAc analogs for suppression of mouse and human pro-inflammatory and autoimmune T cell responses in vitro. Specific Aim 3 will investigate oral delivery of GlcNAc analogs in mice that best increase N-glycan branching to suppress autoimmune T cell responses and treat mouse models of MS. In a future Phase II proposal, the single best analog will be targeted for development, including detailed in vivo toxicology and pharmacokinetic studies leading to a Phase 1 clinical trial. Our goal is to develop the first oral therapeutic that directly targets an underlying molecular and genetic defect that promotes autoimmune pathogenesis in MS.